Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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710 FXUS63 KDTX 130504 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 104 AM EDT Mon May 13 2024 .KEY MESSAGES... - Showers and scattered thunderstorms increasingly likely throughout Monday morning as a cold front drops through the region. This first round of precipitation will be favored along or north of M59. - Renewed rainfall, heavy at times, is possible Monday afternoon into Tuesday morning as the front stalls across central Lower Michigan. - Showers and thunderstorms continue Tuesday as the front exits the region. Cooler than normal temperatures follow Tuesday and Wednesday. && .AVIATION... Broken line of showers with a handful of embedded thunderstorms is working into northwestern portions of the area at forecast period start time. Thunder has already crossed MBS with scattered shower activity expected to linger through ~09Z. To the south, FNT has the best potential to see thunder though a weakening trend has been noted in the line as it crosses central MI. Have continued to only include shower mentions for PTK/FNT given the lowered confidence, instead amending as needed if storms maintain themselves. Similarly, weakening trend lends low confidence in rain reaching the Detroit terminals late tonight. Frontal zone looks to linger near the northern TAF sites (MBS/FNT) today offering additional rain chances this afternoon-evening. Areas south have a good shot at remaining dry until evening when the front starts to sag south again. For DTW/D21 Convection...Remnant convection starting to enter the northern portions of the D21 airspace. The best potential for thunder will be towards FNT as weakening trend lends lower confidence for DTW early this morning. DTW shower/storm chances still expected to hold off until late evening/tonight (after 02Z). Worth noting, some storms possible late this afternoon over northernmost portions of D21 airspace. DTW THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 351 PM EDT Sun May 12 2024 NVA in the wake of the departing upper-level trough has bolstered deep layer subsidence through the afternoon, promoting generally clear skies which have allowed temperatures to peak into the upper 60s to lower 70s, outside of the Thumb with the lake induced thermal influence. A prominent but narrow corridor of mid-level clouds will briefly filter in across SE MI through the later afternoon and evening hours along the edge of a weak and fleeting shortwave, with a warm front then pushing in shortly after the departure of the wave. The 12Z DTX RAOB displays a prominent dry layer from h850 which is maximized up around h500. Precipitation is not expected with either of these features. The potential for rain and thunderstorm chances will be centered late tonight into tomorrow morning (04Z - 12Z) along a cold front, which is projected to push through central lower Michigan before stalling. The expansion of the llj along the frontal boundary will elongate hodographs which will support moderate, partly crosswise low to mid-level shear with otherwise weak deep layer shear. However as is typical with unfavorable nocturnal timing of cold fronts, SBCAPE values will be nil with MUCAPES aob 500 J/kg and the effective inflow layer will be above the surface thus only an elevated portion of the shear profile can be realized. The severe weather threat will be very low given the above, but with some elevated CAPE and mid-level lapse rates ranging between 6-7 C/km, thunderstorms will be possible within the line. SWODY1 clips the northwest portion of Midland and Bay Counties within a marginal risk. If storms overachieve, hail up to an inch would the primary threat given the projected elevated nature of activity. This frontal boundary will be the focal point for renewed rain and thunderstorm chances by tomorrow afternoon, with the vast majority of model guidance places this boundary just north of M59, falling somewhere along the Flint-Tri Cities-Thumb region. PW values are not remarkable in the sense that they fall within climatological norms, however, near parallel cloud depth/shear vectors relative to the boundary coupled with the enhanced theta-e environment with MLCAPE values rising between 500-1000 J/kg supports the potential for repeated rainfall, heavy at times with any convective activity. The Metro region down into the border is favored to stay dry for at least the first half of the day given it is entrenched in the warm sector away from the boundary, but rain and possible thunderstorm chances turn more likely late tomorrow night into Tuesday once both the low pressure fills in across the Tennessee Valley while the cold front then starts to move southeast in response to the building high pressure system over Ontario. Have bumped up daytime high temperatures to or slightly above 80 degrees across the Metro region given higher confidence for rainfall to hold off into later on in the day. Precipitation chances continue into Wednesday morning, before high pressure fills in across the Great Lakes. Please see the hydrology section for additional information. A building shortwave ridge will help support dry conditions through Thursday, with the next chance for showers and thunderstorms entering Friday and Saturday, initially from a shortwave, with a possible low pressure system impacting the state by the start of the weekend. Confidence on the development and position of low pressure system is very low at this time with large variance noted between ensembles. MARINE... High pressure today maintains dry weather and light southerly flow. The next low pressure system however will gain influence overnight with rain moving in ahead of a stalling cold front. As the front stalls, expect continued rain showers especially for locations within and south of Lake Huron. Slow progression of the cold front lends to a gradual shift to northwest flow by Tuesday evening. High pressure then moves in Wednesday to afford drier weather for mid- week. There may be a need for localized Small Craft Advisories late Tuesday-Wednesday as wind gusts and waves ramp up. HYDROLOGY... An active period of weather will be centered on a cold front moving into Lower Michigan late tonight which then stalls in central to southern Lower Michigan Monday and Monday night. Showers and thunderstorms will be numerous along the front, especially Monday evening and early Tuesday morning, when locally heavy rainfall totaling 1-2 inches is possible. Predictability is moderate on this overall rainfall scenario (numerous showers and some thunderstorms along the front), but still low on precisely where the front will line up. The current guidance suggests the frontal boundary stalling north of M59, likely across the Tri-Cities to Thumb. A broad area of minor flooding potential is centered on the Monday night to Tuesday morning time period for Southeast Michigan. PREV DISCUSSION... Issued at 331 PM EDT Sun May 12 2024 && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....KDK DISCUSSION...AM MARINE.......MV HYDROLOGY....AM You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.